To open the vent on the house on Toupee Terrace you need the Laser pen. You get it from the First Spy rescued at the Docks, The spy on Toupee Terrace is the Second Spy.
(see related question)
you click on it and you will use the laser pen
On The Spy Island!
it is on top of the vault
In the kitchen you have to jump to the ceiling and go through the vent until you reach the door.
you have to find an air vent and go threw it1
The tallest building on Balding Avenue. It is where the third spy is held. (see related question)
its easy just google the thing u want to find
The kitchen vent in the Bistro, just jump up. The vent atop the electrified building has bars on it. You will need to get the Laser Pen by rescuing the First Spy on the docks.
go through the vent
you go to the kitchen and jump up until u see a vent go in the vent and then there will be lights jump on the lights till there are no more
The electrified building on Toupee Terrace is where you will find the second missing spy. Before you can rescue him, you have to save the first spy at the Docks. The first spy will give you the Laser Pen that can cut through the bars on the roof window.
Climb up the inside of the kitchen vent, then across the light fixtures to the door.